If you use Malwarebytes it can block websites. If you want it to stop blocking your favorites sites, try this:

Malwarebytes blocked access to potentially malicious website

If you are visiting websites and have Malwarebytes Anti-malware running it can happen that it blocks certain websites. Most of the time these sites are malware sites. However, there are many false positives.

To stop Malwarebytes from blocking your websites, wait until the popup appears that the website has been blocked and then right-click on the Malwarebytes tray icon and click on add to Ignore list:

Stop malwarebytes from blocking sites

However, this does not always work. If it does not work, disable the Malwarebytes protection temporarily or permanently:

Right-click on the tray icon and uncheck Enable Protection

Disable malwarebytes protection